Investigation of interfacial crystallization fouling behaviors and membrane re-functionalization based on a long-distance membrane distillation module

Abstract

Membrane distillation technique can be applicable for the treatment of highly concentrated aqueous solutions. Crystallization and fouling on the membrane surface are important issues during a membrane distillation process, which significantly affect its separation performance. Crystallization precipitation is a gradual process along the normal direction of the membrane and the feed flow direction. It is not easy to observe the gradual behavior in a relatively small module with a short flow distance in common lab scale modules. In this work, a long-distance membrane distillation module (~2 m in length) was designed and set up to investigate the gradual evolutionary process of crystallization fouling on the porous membrane. A practical model was proposed to estimate the approximate position of crystallization fouling in a long-distance membrane distillation process based on multiple factors including operating parameters and intrinsic membrane properties. A set of proof-of-principle experiments were proceeded to observe and characterize the crystallization fouling behaviors on the membrane surface and inside the pores under various conditions. Furthermore, to re-functionalize the membrane distillation system with the membrane fully covered by salt crystals, flushing the system with pure water was applied. The performance of the re-functionalized system was also investigated.